Moles and equivalents are closely rated. Equivalents consider the valence charge of the ion, either positive or negative, but 1, 2, or 3 electron charges:
Charge of +1 or -1: 1 mole = 1 equiv.
Charge of +2 or -2: 1 mole = 2 equiv.
Charge of +3 or -3: 1 mole = 3 equiv.
Basically 1 equivalent is one mole of electrons transfered between a donor and acceptor.
As JohnS says, it depends on the valencies of the species involved. However, it can be a bit more complicated than that, as it takes into account the molecule or ion involved, and the number of electrons required to balance the electronic (chemical) equation to produce the material of interest.
For example, producing ammonia from nitrate:
NO3(-) + 10H+ + 8e- gives NH4(+) + 3H2O, so 8 eqivalents per mole of Nitrate.
Maybe. It depends. An equivalent is a mole of electrons passed in a reference reaction. It depends on the ionic charge of the substance of interest (and in more complex cases, on the reaction) See post #2.